A sulfate-reducing bacterium is a bacterium that oxidizes an organic substance with a sulfate ion as an electron acceptor to acquire energy. The growth temperature range of the sulfate-reducing bacterium is different depending on the kind thereof, and thermophilic bacteria, mesophilic bacteria, psychrotrophic bacteria, and psychrophilic bacteria are present. Moreover, depending on the difference in growth pH, bacteria that grow well around a neutral pH range and bacteria that grow well under an acidic or alkaline condition are present. Moreover, their living areas cover a wide range such as the inside of see mud, general soil, hot water-spurting areas, pipe lines, and so on.
In the process of acquiring energy of the sulfate-reducing bacterium, hydrogen sulfide as a reductant of a sulfate ion is produced. The hydrogen sulfide is a substance that has strong toxicity and corrosiveness and emits offensive odor, and therefore a problem arises when a large amount of hydrogen sulfide is produced. For example, hydrogen sulfide is generated when the sulfate-reducing bacterium acquires energy making use of a sulfate ion as an electron acceptor that is contained in natural water, fertilizers (ammonium sulfate and so on), or the like and problems that the generated hydrogen sulfide inhibits the growth of crops in agricultural fields and corrodes ion materials (underground pipes and so on) have been known.
Moreover, the generation of hydrogen sulfide a sulfur source of which is illegally dumped gypsum has become a problem in recent years. It is known that the hydrogen sulfide generation is associated with the sulfate-reducing bacterium.
The hydrogen sulfide generation from a waste gypsum plasterboard has been reported as an example of the hydrogen sulfide generation due to the sulfate-reducing bacterium. The waste gypsum plasterboard contains paste and paper (nutrients) in addition to calcium sulfate (sulfate ion) that is a main component. Accordingly, it sometimes occurs that the sulfate-reducing bacterium in soil assimilates the waste gypsum plasterboard resulting in hydrogen sulfide generation.
Thus, attempts have been made to inhibit the proliferation of the sulfate-reducing bacterium to thereby suppress the hydrogen sulfide production. For example, the present applicant has disclosed a method for inhibiting proliferation of a sulfate-reducing bacterium to thereby suppress hydrogen sulfide generation by adding an anthraquinone compound to a soil-treating material that contains gypsum as a main component (see, Patent Literature 1).
However, since the anthraquinone compound that is extremely expensive is used in the technology described in Patent Literature 1, there has been a problem in terms of production cost. The actual circumstance is that the utilization of the technology has not widely been spread with the cost being an obstacle particularly in applications such as a soil-treating material where a large amount of anthraquinone compound is used.
Thus the present applicant has also disclosed a method for inhibiting proliferation of a sulfate-reducing bacterium to thereby suppress the hydrogen sulfide generation by adding a specified aluminum compound such as a hydrate of aluminum sulfate [Al2(SO4)3.nH2O (n=6, 10, 16, 18, or 27] to a gypsum composition (see, Patent Literature 2).